package main

import (
	"fmt"
)

type MyError struct {
	What string
}

func (e *MyError) Error() string {
	return fmt.Sprintf("at %s", e.What)
}

func run() error {
	return &MyError{"it didn't work"}
}

func Sqrt(x float64) (float64, error) {
	return 0, nil
}

func main() {
	if err := run(); err != nil {
		fmt.Println(err)
	}

	fmt.Println(Sqrt(2))
	fmt.Println(Sqrt(-2))
}
